Method for forming thin film

Abstract

Method for forming a thin film at low temperature by using plasma pulses is disclosed. While a purge gas or a reactant purge gas activated by plasma is continuously supplied into a reactor, a source gas is supplied intermittently into the reactor during which period plasma is generated in the reactor so that the source gas and the purge gas activated by plasma reacts, so that a thin film is formed according to the method. Also, a method for forming a thin layer of film containing a plural of metallic elements, a method for forming a thin metallic film containing varied contents by amount of the metallic elements by using a supercycle T supercycle comprising a combination of simple gas supply cycles T cycle , . . . , and a method for forming a thin film containing continuously varying compositions of the constituent elements by using a supercycle T supercycle comprising a combination of simple gas supply cycles T cycle , . . . , are disclosed. The methods for forming thin films disclosed here allows to shorten the purge cycle duration even if the reactivity between the source gases is high, to reduce the contaminants caused by the gas remaining in the reactor, to form a thin film at low temperature even if the reactivity between the source gases is low, and also to increase the rate of thin film formation.

1 . A method for forming a thin film comprising: 
 (a) supplying a first source gas to a reactor loaded with a substrate in which reactor a reaction for forming said thin film takes place,    (b) stopping supply of said first source gas and purging said first source gas remaining in said reactor,    (c) supplying a second source gas to said reactor, wherein radio frequency (RF) electric power is applied during the supply period of said second source gas to activate said second source gas, and    (d) turning said RF electric power off and stopping the supply of said second source gas,    wherein a purge gas is continuously supplied while the steps (a) through (d) are processed to form said thin film.    
     
     
         2 . The method of  claim 1 , wherein processing the steps of (a) through (d) are repeated a predetermined number of times.  
     
     
         3 . The method of  claim 1 , further comprising: 
 purging the activated second source gas remaining in said reactor after the step (d),    wherein said purge gas is supplied continuously while purging the activated second source gas.    
     
     
         4 . The method of  claim 1 , wherein the step (d) comprises the processes of turning the RF electric power off and stopping supply of said second source gas after a predetermined duration of time, 
 wherein said purge gas is continuously supplied while said second source gas is being supplied after said RF electric power is turned off.    
     
     
         5 . The method of  claim 1 , wherein said first source gas contains a constituent element of a thin film to be formed, and does not react with said purge gas.  
     
     
         6 . The method of  claim 1 , wherein said second source gas contains a constituent element of a thin film to be formed, does not react with said purge gas, and does not react with inactivated first source gas.  
     
     
         7 . The method of  claim 1 , after the step (d) further comprising: 
 (e) supplying a third source gas to said reactor;    (f) stopping supply of a third source gas and purging said third source gas remaining in said reactor,    (g) supplying said second source gas to said reactor, wherein RF electric power is applied during the supply period of said second source gas so that said second source gas is activated, and    (h) stopping supply of said RF electric power and said second source gas,    wherein said purge gas is continuously supplied while the steps (e) through (h) are processed to form said thin film.    
     
     
         8 . The method of  claim 7 , wherein the steps (a) through (h) are processed m times and the steps (a) through (d) are processed n times and these processes are repeated to form a thin film having a constituent element of said first source gas, wherein said thin film formed contains more constituent element in amount than that in a thin film formed by repeating the steps (a) through (h), and where m and n are natural numbers equal to or larger than 1 and m is larger than n.  
     
     
         9 . The method of  claim 7 , wherein a thin film is formed by processing the steps (a) through (h) m times and processing the steps (a) through (d) n times and the entire process is repeated to form a thin film, thereby the composition of said thin film formed is continuously varied by setting the values of m and n to natural numbers including 0(zero) instead of fixing them.  
     
     
         10 . The method of  claim 7 , wherein each one of the steps of (d) through (h) comprises the step of stopping supply of said second source gas after a predetermined period of time from the time when said RF electric power is turned off, and wherein said purge gas is continuously supplied to said reactor while supplying said second source gas after said RF electric power is turned off.  
     
     
         11 . The method of  claim 7 , further comprising: 
 purging the activated second source gas remaining in said reactor, after the step (d) and before the step (e), and    purging the activated second source gas remaining in said reactor after the step (h),    wherein said purge gas is continuously supplied while said activated second source gas is being purged.    
     
     
         12 . The method of  claim 7 , wherein a third source gas contains a constituent element of a thin film to be formed, does not react with said purge gas, and does not react with inactivated second source gas.  
     
     
         13 . A method for forming a thin film, while supplying a reactant purge gas continuously into a reactor loaded with a substrate, comprising: 
 (A) supplying a source gas to a reactor loaded with a substrate,    (B) stopping supply of said source gas and purging said source gas remaining in said reactor;    (C) turning on the RF electric power to activate said reactant purge gas; and    (D) turning off said RF electric power,    wherein said reactant purge gas is continuously supplied into said reactor loaded with a substrate, in which reactor a reaction for forming a thin film takes place while processing the steps (A) through (D).    
     
     
         14 . The method of  claim 13 , wherein the steps (A) through (D) are repeated a predetermined number of times.  
     
     
         15 . The method of  claim 13 , further comprising: 
 purging the activated reactant purge gas remaining in said reactor after the step (D),    wherein said reactant purge gas is continuously supplied into said reactor while said activated reactant purge gas is being purged.    
     
     
         16 . The method of  claim 13 , wherein said source gas contains a constituent element of a thin film to be formed, and does not react with the inactivated reactant purge gas.  
     
     
         17 . The method of  claim 13 , wherein said reactant purge gas contains a constituent element of a thin film to be formed, and does not react with said source gas without plasma, but reacts with the source gas with plasma-assisted activation.  
     
     
         18 . The method of  claim 13  after the step (D), further comprising: 
 (E) supplying a second source gas into said reactor loaded with a substrate,    (F) stopping supply of said second source gas and purging said second source gas remaining in said reactor,    (G) turning on the RF electric power to activate said reactant purge gas, and    (H) turning off the RF electric power,    wherein said reactant purge gas is continuously supplied into said reactor while the steps (E) through (H) are being processed.    
     
     
         19 . The method of  claim 18 , wherein the steps (A) through (H) are processed m times and the steps (A) through (D) are processed m times, and then both processes are repeated to form a thin film containing a constituent element of said first source gas more content by amount than that in a thin film formed by repeating the steps (A) through (H), wherein m and n are natural numbers equal to or greater than 1 and m is greater than n.  
     
     
         20 . The method of  claim 18 , wherein the steps (A) through (H) are processed m times, and the steps (A) through (D) n times and then both processes are repeated to form a thin film in such a way that the composition of said thin film formed is gradually and continuously changed by varying the numbers of repetitions m and n from zero(0) to natural numbers.  
     
     
         21 . The method of  claim 18  further comprising: 
 purging said activated reactant purge gas remaining in said reactor after the step (d), and    purging the activated reactant purge gas remaining in said reactor after the step (H),    wherein said reactant purge gas is continuously supplied into said reactor while said activated reactant purge gas is being purge.    
     
     
         22 . The method of  claim 18 , wherein said second source gas contains a constituent element of a thin film to be formed, and does not react with said inactivated reactant purge gas.